I'm 12 days in to IP I have been very strict with this plan.

Today I was at a friends house, and she offered me a coffee, which I said ok to, and she poured me a cup and then put in 1tsp of sugar. as that is my usual.

Is this going to mess me up? I feel bad because I should have told her no to the sugar.

Will drinking more water today help flush that out? or did I mess up big time?

Thanks Krystal

You will be fine. If you have not had a restricted today, replace it with a non restricted.
Continue on otherwise.

The best thing to do is just start fresh and don't stress about it. It may set you back a little, but worse would be giving in to it again, or giving up. You don't sound like that's where you are at mentally so just finish out your day 100% OP, and treat tomorrow like a new day.

Water won't flush it out, you just have to push forward.

Thanks so much scorbett! that's reassuring, the 12 days I have been OP and Have been strict with myself, I have to get used to saying No sugar next time I'm at a friend visiting, thank goodness it was only 1 cup of coffee with sugar.

You're welcome It's hard when you first start, to know how to say "no" to things without getting odd reactions from people. But it DOES get easier! The first time I had coffee with my SIL after starting, she automatically poured my usual "coffeemate with a splash of coffee". I felt bad having to pass and pour myself a fresh cup, and she definitely gave me a look when I drank it black...but now she LIKES setting my coffee aside because she knows she's helping my success!